This invention relates to an apparatus for measuring the length of movement of a continuous stock material strip which is intermittently fed to a press by feed rollers and, more particularly, to such an apparatus which includes a bridge assembly for correcting successive lengths of movement of the intermittently fed stock material strip by varying the distance the strip travels from the feed rollers to the press.
Apparatus has been employed in the prior art for determining a length of movement of a strip of material as the strip is intermittently fed by feed rollers into a press. For example, U.S. Pat. No. 3,709,078 discloses an apparatus for sensing the length of movement of an intermittently fed strip of material. The apparatus comprises rotor means including a shaft which rotatably supports two wheels that engage the strip of material. Intermediate the ends of the shaft is a rotor which includes a conductor section and an insulator section. A plurality of brushes are provided for sensing the rotative position of the rotor, thereby providing an indication of the length of movement of the strip. Also provided on the shaft is a collar having an opening therein. A spring-biased plunger is provided which is engageable with the opening in the collar when the press closes. If the strip of material has been fed a correct distance, the opening in the collar will be positioned directly in alignment with the plunger which will move freely into the opening when the press closes. If, however, the strip has been fed a distance either slightly farther or less than intended, the opening in the collar will be slightly out of alignment with the plunger. Thus, when the press closes, the plunger will be forced into the opening in the collar, thereby rotating the shaft and the wheels positioned thereon. Rotation of the wheels is intended to move the strip so as to correctly position the strip in the press. It has been found, however, that slippage occurs between the wheels and the strip as the shaft begins to rotate causing inaccurate correction of the position of the strip. The apparatus has also been found to be disadvantageous since an operator must engage in a tedious, time consuming operation of changing the wheels on the shaft each time a different length of feed is desired.
Accordingly, there is a need for an accurate and easily operable apparatus for measuring and controlling lengths of movement of a continuous stock material strip which is intermittently fed to a press by a set of feed rollers.